Waste heat recovery has become very important in the last decennia. The Organic Rankine Cycle (ORC) is the most popular technology to transform waste heat into mechanical work or electricity. While large and medium scale installations are widely available on the market for various (fixed) temperature and power levels, small scale ORC's are still in a pre-commercial phase, probably because of a relatively high specific price. To make small scale ORC's more technically and commercially attractive, the price needs to be reduced and/or the performance has to be increased, or other technical advantages need to be provided.
FIG. 1 shows a block-diagram of an ORC installation, known in the art. The functioning of such an installation, and in particular the thermodynamic aspects thereof are well known in the art, and hence need not be described in detail herein. The present invention focuses on two components of such an installation: the expander (2) and the generator (3), and proposes a particular architecture for these devices.
WO2008154730A1 discloses an energy transfer machine and method for producing power or cooling from low grade heat sources. In FIG. 38 of the present invention, which is a replica of FIG. 11 of said international patent application, an energy transfer machine 1000 is shown comprising a piston 1150 which spins around its axis while reciprocating. The device 1000 has two chambers 1171, 1172, two separate inlet ports 1132A, 1132B and two separate output ports 1131A, 1131B. In the position shown in FIG. 38, fluid present in the chamber 1171 leaves the device via outlet port 1131A by flowing through a “flow conduit” 1199A being a groove formed in an outer wall surface of said piston. After rotation of the piston, the groove comes in fluid connection with the inlet port 1132A, and fluid enters the chamber 1171 via the same groove.
Although many types of expanders are known in the art, there is still room for alternatives and/or for improvement. Expanders and compressors are seen as the inverse of each other, some of the challenges encountered for expanders are also faced in the design of compressors.